Critique Request - Millenium Hops?

So, I'd like to try to develop a cheaper version of this batch that I'm drinking. My goal is to develop a recipe that results in a good session all-purpose ale, suitable for pretty much anything.

My original recipe calls for 2oz Challenger & 1 oz First Gold; but I'm seeing where I can buy a pound of "Millenium" hops on the cheap and wondering if I'm going to notice *that* much of a difference.

Here's my amended potential recipe:

6# Pilsen DME
12 oz. Crystal Malt (thinking 20L to keep it light colored)

0.5 oz. Millenium (60m) - avg. 15.5% AU
0.25 oz Millenium (15m)
0.25 oz Millenium (1m)

15m. 1oz Irish moss

Munton's Dry Ale Yeast

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target OG: 1.058
target FG: 1.016
bitterness: 7.8 HBU / 26.9 IBU

-- according to Beer Calculus . homebrew recipe calculator, this is *pretty darn near* what I'm currently drinking as far as bitterness, so my real question is, has anyone used Millenium for *both* bittering and aroma, and is there going to be that much of a noticeable difference between using solely Millenium vs. the Challenger/First Gold combo?

This would take my cost from $45/batch down to $25/batch if I do some creative shopping, so I'm real tempted to experiment -- but, no price drop does me any good if I get myself into a "DMS" situation.

Thanks in advance for any comments/advice/anecdotal help...